The synthesis of nitroxide spin labels of cortisol and related steroidal hormones is being investigated; currently, spin-labeled esters of cortisol and testosterone (esterfied at the C-12 position of cortisol and the C-17 position of testosterone) have been synthesized. Attempts to attach the nitroxide moiety at other positions of the cortisol molecule have thus far been unsuccessful, but additional studies toward this goal are currently in progress. Studies are in progress to determine the extent to which each of the above spin labels binds to corticosteroid-binding globulin (CBG), which is present in blood serum. If one or more of these spin labels has a high affinity for binding to CBG, studies will be initiated to develop an analytical method of analyzing for the level of CBG in blood serum using these spin labels and esr spectroscopy.